Blood tests for food intolerances are wildly unreliable. These blood tests look for IgG antibodies, which are a marker of exposure to food proteins, not an indicator of an allergy or intolerance. So when blood testing comes back with a long list of foods that you are supposedly intolerant of, don’t be surprised that all the foods on the list are foods you consume regularly and/or ate recently! Some research indicates that the presence of IgG antibodies may even be a marker of food tolerance, not a food intolerance.

Testing at different labs: Different labs have returned different lists of food intolerances to the same people, and results from the same lab for the same person have also given different results. In other words, blood testing produces lots of false positives and false negatives and is not reliable or evidence based.

Breath analysis is the one method of testing that can reliably identify just one type of food intolerance, which is the malabsorption of certain sugars or carbohydrates.

My new book The Athlete’s Fix will help you find your problem foods—and the foods that make you feel and perform your best. The Athlete's Fix offers a sensible, three-step program to identify food intolerances, navigate popular special diets, and develop your own customized clean diet that will support better health and performance.